1. Field of the Invention:
This invention relates to a means for accurately locating and clamping a jig fixture onto the bed or platen of, for example, a milling machine and, more particularly, to a means that is simple, positive, durable and rugged for use with relatively large and heavy jigs of various sizes and shapes.
2. Description of the Prior Art:
Machine tools such as milling machines typically include a work bed on which the workpiece is held while it is being milled. In order for the machining operation to be carried out accurately, it is necessary for the workpiece to be positioned precisely on the work bed relative to the cutting tool. In the past, various types of jigs and other fixtures have been used to provide stop surfaces against which the workpiece can be held to locate it in the proper location.
However the problem is more complicated whenever the workpiece is relatively large, heavy and clumbersome and the workpiece must be transferred from one type of cutting machine to another type and sometimes back to the first machine. To help solve this problem the workpiece would be clamped within a specially designed jig or fixture. Since the beds onto which the jigs are to be positioned are planar the jig is design with a complementary flat or planar surface. In addition, such beds have recessed therein a plurality of criss-cross straight grooves. Accurately positioned, cylindrical and perpendicular holes are formed in the flat surface of the jig, in which holes are fixed dowels or fixture keys extending out from the surface. To set up the workpiece for maching, the jig is supported over the cutting tool bed and carefully lowered onto the bed. By sight one has to make sure that each key is carefully aligned with a respective groove. The jig is locked in place when engagement is made between the dowels and grooves.
The disadvantage in this method is that, if the respective key is not fully aligned with its respective groove, damage is done to the dowels and to the tool bed because the weight of the jig would now be concentrated on a relatively small area. Damaged dowels or keys are cheaply replaced but a damaged tool bed requires expensive repair work.
The following United States Patent were uncovered: U.S. Pat. Nos. 744,559; 2,472,083; 2,676,413; 2,707,419; 3,049,345; 3,063,705; 3,554,530; 3,942,780; 3,967,816; 4,577,847 & 4,664,366. Although they teach means for "holding down" a work piece for machining, they do not suggest that the means described herein could or should be used.